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Knowledge of the sex ratio of a population is crucial to understand their structure and dynamics. For species, such as marine turtles, with temperature-dependent sex determination, this knowledge provides a baseline in advance of climate change. Determining the primary sex ratio for marine turtle populations is challenging since offspring lack sexually dimorphic external characteristics. Therefore several proxies have been used to estimate the primary sex ratio of marine turtle populations. However, no study to date has compared estimations of sex ratio when using different proxies to determine the most accurate and to detect potential bias. To address this, we estimated the sex ratio of natural loggerhead, Caretta caretta, nests using 8 different proxies: two based on constant temperature equivalent (average of temperature or average temperature weighted by the growth of embryos during each time step) both for three developmental periods (the whole incubation, the middle third of incubation and the middle third of development) as well as two proxies based on incubation duration (duration of the whole incubation and of the middle third of development). Sex ratio estimates differed greatly depending on the proxy being used. Here we discuss the differences among proxies based on the biological relevance of underlying hypotheses and highlight the need for studies to accurately determine the thermosensitive period and to obtain appropriate estimates of embryo growth rate to estimate marine turtle sex ratio.

Bacterial type VI secretion systems (T6SSs) are molecular weapons designed to deliver toxic effectors into prey cells. These nanomachines have an important role in inter-bacterial competition and provide advantages to T6SS active strains in polymicrobial environments. Here we analyze the genome of the biocontrol agent Pseudomonas putida KT2440 and identify three T6SS gene clusters (K1-, K2- and K3-T6SS). Besides, 10 T6SS effector-immunity pairs were found, including putative nucleases and pore-forming colicins. We show that the K1-T6SS is a potent antibacterial device, which secretes a toxic Rhs-type effector Tke2. Remarkably, P. putida eradicates a broad range of bacteria in a K1-T6SS-dependent manner, including resilient phytopathogens, which demonstrates that the T6SS is instrumental to empower P. putida to fight against competitors. Furthermore, we observed a drastically reduced necrosis on the leaves of Nicotiana benthamiana during co-infection with P. putida and Xanthomonas campestris. Such protection is dependent on the activity of the P. putida T6SS. Many routes have been explored to develop biocontrol agents capable of manipulating the microbial composition of the rhizosphere and phyllosphere. Here we unveil a novel mechanism for plant biocontrol, which needs to be considered for the selection of plant wardens whose mission is to prevent phytopathogen infections., We thank Milagros Lopez (IVIA, Spain) for providing X. campestris and P. carotovorum, Martin Buck (Imperial College London, UK) for P. syringae and Ehr Min Lai (Academia Sinica, Taiwan) for A. tumefaciens and the pRL662-gpf. We thank Tom Wood for kindly providing the T6SS scheme shown in Figure 1a. PB is supported by the Spanish Ministry of Economy through Juan de la Cierva grant (JCI-2010-06615), by the Andalusian Knowledge Agency through a Talent Hub grant (TAHUB-010) and by an EMBO short-term fellowship. MAL is supported by the Spanish Ministry of Economy through a Ramon&Cajal grant (RYC2011-08874). AF is supported by a BBSRC grant (BB/N002539/1). LA is supported by a BBSRC grant (BB/N002539/1) and a Marie curie Fellowship (PIIF-GA-2012-328261).